Drawing on classical and contemporary theories of power, this paper traces the development of relational conceptions of power through Marx and Weber. In doing so it traces sociological constructs of power as benefit and control to the classical conceptions of Marx and Weber respectively and finds the origin of contemporary structural conceptions in their analyses of power. The paper finds that "separation," a pivotal condition for Marx and Weber, is fundamental to contemporary conceptions of structural power in network exchange: The condition of "separation" upon which both Marx and Weber focused (separation of workers from the means of production, separation of officials from the means of administration) is shown to be linked to the structural power condition "exclusion," discovered in experimental network exchange research. The convergence of sociological constructs of power on separation and exclusion as such is discussed. Does this convergence suggest that the two are distinctly modern conditions of power?